Prompt Security is a capable enterprise AI gateway — now part of SentinelOne — that inspects LLM traffic through the browser and a cloud service, with an on-premises SKU announced in 2026 for disconnected environments. The default cloud delivery reintroduces the SC.3.177 transit problem for regulated data; the on-prem option removes it, but arrives as an enterprise platform SKU through enterprise procurement.
| Dimension | HoundShield | Prompt Security |
|---|---|---|
| Where prompts are scanned | Locally by default (Mode B/C) | Cloud service by default; on-prem as enterprise SKU |
| Pricing model | $499 report + per-org plans | Per-seat, enterprise-quoted |
| Prompt-injection / shadow-AI detection | Prompt scanning + audit; injection on roadmap | Mature |
| CMMC / NIST 800-171 evidence PDF | $499 one-time, control-mapped | Not a deliverable |
| Air-gapped deployment | Yes (Mode C), self-serve | On-prem SKU announced (2026), enterprise procurement |
| Best-fit org size | 50–500 employees, regulated | Large enterprise |
Comparison based on publicly available information, last reviewed 2026-07-04. Competitor facts change — tell us if anything here is out of date.
Prompt Security sits between employees and AI apps (browser extension + proxy), inspecting prompts and responses for sensitive data, prompt injection, and shadow-AI usage. It is delivered primarily as a managed cloud service; following the SentinelOne acquisition it sits inside a broader enterprise security suite, and SentinelOne has announced an on-premises version aimed at disconnected and air-gapped environments. Confirm current deployment options and pricing with their team.
HoundShield Mode B keeps prompt content on your own infrastructure by design and by default — $499 self-serve, Docker, minutes to deploy. SentinelOne's on-prem Prompt Security SKU validates the architecture, but it ships as an enterprise platform purchase; their default cloud delivery still routes inspection through their service, which for CUI is the exposure you're trying to remove.
Per-seat AI-gateway pricing scales painfully for a 50–500 person contractor. HoundShield leads with a $499 one-time report and per-org plans.
HoundShield's report is mapped to NIST 800-171 Rev 2 and formatted for a C3PAO. A general enterprise AI gateway is not a CMMC deliverable.
Below the enterprise threshold and inside isolated networks, HoundShield deploys where a cloud enterprise suite won't.
Who this matters most for: Sub-500-employee defense and legal firms (Jordan, Marcus) that need CMMC evidence without enterprise per-seat pricing or cloud inspection.
HoundShield scans prompts locally in under 10ms. That CUI-safe property holds only when the scanner runs inside your own boundary. Pick the deployment mode that matches your data:
A · Hosted trial
On Vercel — not FedRAMP-authorized. Demo and non-CUI evaluation only.
B · Self-hosted Docker
Your own infrastructure. CUI-safe — prompt content never leaves your boundary. Right for CUI-handling contractors.
C · Air-gapped
Isolated network. CUI-safe. For enterprise / IL-5+ environments.
HoundShield vs Prompt Security
Still have questions? Talk to a compliance engineer — we respond within 4 business hours.
Run HoundShield locally for 14 days and get a $499 CMMC AI Risk Assessment PDF — no prompt content ever leaves your network.